The present invention relates to an image forming apparatus and an image forming method of supplying recovered toner into a developing device and reusing it, and they can be applied to an image forming apparatus and the like of, for example, a copy machine, printer, facsimile, and the like.
An image forming apparatus having a toner recycle device executes an image forming process such that the surface of a photosensitive drum is charged negatively, a latent image is formed by exposing the photosensitive drum with laser beams based on an image signal (a surface is charged with a potential), a visible image is formed by causing the latent image to absorb negatively charged toner, and the visible image is transferred onto a positively charged sheet and fixed thereon.
In the above image formation, toner, which was already used for image formation and collected for recycle (hereinafter, referred to as xe2x80x9crecovered tonerxe2x80x9d), and new toner, which is not yet used for image formation (hereinafter, referred to as xe2x80x9cnew tonerxe2x80x9d), are used in mixture. That is, the recovered toner is recycled. The recovered toner is recycled by a toner recycle device.
A conventional toner recycle device is controlled to replenish recovered toner within a range in which a stable image is not damaged. That is, the toner recycle device is controlled to form an image stably by automatically changing the amount of the recovered toner to be replenished by, for example, reducing the amount of the recovered toner or stopping the supply of the recovered toner in accordance with a set value of the toner ratio density of an developing agent in a developing device.
In contrast, there is a case in which it is desired to make a large number of copies at any cost regardless of that new toner remains in a very small amount (new toner remains in a small amount) and that spare new toner is not available at hand. Even in such a case, however, the copies must be waited until the spare new toner is obtained.
An object of the present invention is to extend a period until toner is exhausted by reducing the amount of consumption of new toner when the new toner remains in a small amount or when it is desired to save the new toner. That is, the object of the present invention is to extend the period until the toner is exhausted by selecting a new toner saving mode by the intention of a user or automatically without waiting for spare new toner even in a case in which it is desired to make copies in a large amount after the amount of the new toner is greatly reduced, and the like. Further, when the user desires to save the amount of consumption of the new toner as mush as possible while he or she does not place greater emphasis on the quality of an image as long as characters can be read, the user extends the period until the toner is exhausted by selecting the new toner saving mode by his or her intention. In contrast, another object of the present invention is to execute a scattering of toner prevention means because the toner is scattered in an increased amount when recovered toner is supplied in a large amount to save the new toner.
The image forming apparatus and the image forming method of the present invention, which have been made to achieve the above objects, reduce the amount of the new toner to be supplied into a developing device. Further, as the remaining amount of the new toner to be supplied into the developing device reduces, the image forming apparatus and the image forming method execute one or a plurality of the following three processing steps of a toner save mode: (1) to increase the ratio of the amount of the recovered toner to be supplied to the amount of the new toner while maintaining the total amount of the recovered toner and the new toner to be supplied into the developing device constant; (2) to reduce the total amount of the recovered toner and the new toner to be supplied; and (3) to stop the new toner to be supplied into the developing device and to supply only the recovered toner.
Further, as the remaining amount of the new toner reduces, an ordinary mode, in which the recovered toner having a preset mixing ratio is mixed with the new toner and reused, is automatically switched or arbitrarily switched manually to the toner save mode.
Furthermore, it is preferable, when the toner save mode is selected, to execute any one or both of means for reducing the rotational speed of a magi-roller of the developing device to prevent the scattering of the toner and means for increasing the amount of charge of the toner so that the toner can be easily absorbed by a latent image on the surface of a photosensitive drum. Further, the timing at which the remaining amount of the new toner is reduced, that is, the timing at which the above processing steps are executed, is preferably the timing at which it is determined that the new toner is remains in a small amount.